U.S. patent application number 10/471264 was filed with the patent office on 2004-06-10 for tower oscillation monitoring device.
Invention is credited to Wobben, Aloys.
Application Number | 20040108729 10/471264 |
Document ID | / |
Family ID | 7677928 |
Filed Date | 2004-06-10 |
United States Patent
Application |
20040108729 |
Kind Code |
A1 |
Wobben, Aloys |
June 10, 2004 |
Tower oscillation monitoring device
Abstract
The present invention concerns a method of controlling a wind
power installation having a control apparatus for operational
management of the wind power installation, in which the
acceleration of the pylon is detected. The invention further
concerns a wind power installation comprising a pylon, a control
apparatus for operational management of the wind power installation
and a device for detecting the acceleration of the pylon. Therefore
the object of the present invention is to develop a method and a
wind power installation of the kind set forth in the opening part
of this specification, in such a way as to implement reliable and
efficient oscillation monitoring in order to open up the
above-mentioned frequency range for operation of the wind power
installation. A method of controlling a wind power installation
comprising a pylon and a control apparatus for operational
management of the wind power installation or parts thereof, wherein
there are provided means with which oscillation of the pylon of the
wind power installation is detected, wherein the means for
detecting the pylon oscillation detect the oscillation travel
and/or the absolute deflection of the pylon in the upper part of
the pylon out of its rest position and the values ascertained by
the means for detecting the pylon oscillation are processed in the
control apparatus, more specifically in such a way that the
operational management of the wind power installation or parts
thereof is altered if the oscillation and/or the absolute
deflection of the pylon exceeds a predeterminable first limit
value.
Inventors: |
Wobben, Aloys; (Agerstrasse,
DE) |
Correspondence
Address: |
Neil Steinberg
Steinbery & Whitt
Suite 1150
2665 Marine Way
Mountain View
CA
94043
US
|
Family ID: |
7677928 |
Appl. No.: |
10/471264 |
Filed: |
January 15, 2004 |
PCT Filed: |
March 14, 2002 |
PCT NO: |
PCT/EP02/02847 |
Current U.S.
Class: |
290/44 |
Current CPC
Class: |
F03D 7/0296 20130101;
F05B 2240/912 20130101; Y02E 10/728 20130101; F03D 7/042 20130101;
F03D 17/00 20160501; F05B 2270/20 20130101; F05B 2270/331 20130101;
Y02E 10/72 20130101; F05B 2260/96 20130101; F05B 2270/334 20130101;
F05B 2270/807 20130101 |
Class at
Publication: |
290/044 |
International
Class: |
F03D 009/00; H02P
009/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 17, 2001 |
DE |
101 13 038.4 |
Claims
1. A method of controlling a wind power installation comprising a
pylon and a control apparatus for operational management of the
wind power installation or parts thereof, wherein there are
provided means with which oscillation of the pylon of the wind
power installation is detected, wherein the means for detecting the
pylon oscillation detect the oscillation travel and/or the absolute
deflection of the pylon in the upper part of the pylon out of its
rest position and the values ascertained by the means for detecting
the pylon oscillation are processed in the control apparatus, more
specifically in such a way that the operational management of the
wind power installation or parts thereof is altered if the
oscillation and/or the absolute deflection of the pylon exceeds a
predeterminable first limit value and two oscillation travels are
detected in at least two different directions in a substantially
horizontal plane.
2. A method according to claim 1 characterised in that the device
for ascertaining the oscillation of the pylon has at least one
acceleration measuring device.
3. A method according to claim 1 or claim 2 characterised in that
the first natural frequency of the pylon is used for ascertaining
the oscillation travel.
4. A method according to one of the preceding claims characterised
in that oscillation travels are detected in at least two different
directions in a substantially horizontal plane.
5. A method according to one of the preceding claims characterised
in that the rotor setting is altered if the oscillation travel
exceeds a predeterminable first limit value.
6. A method according to one of claims 1 to 4 characterised in that
the rotor setting is altered if the oscillation travel exceeds a
predeterminable limit value within a predeterminable period of
time.
7. A method according to claim 6 characterised in that the period
of time is altered in dependence on the magnitude of the
oscillation travel.
8. A method according to one of claims 5 to 7 characterised in that
the rotor is stopped.
9. A method according to one of the preceding claims characterised
in that at least one parameter for ascertaining the oscillation
travel is firstly predetermined and corrected in on-going operation
on the basis of the actually detected measurement values.
10. A method according to one of the preceding claims characterised
in that the oscillation travel is ascertained during a
predeterminable period of time.
11. A wind power installation comprising a pylon and a control
apparatus for operational management of the wind power installation
and a device for detecting the oscillation travel of the pylon.
12. A wind power installation according to claim 11 characterised
in that a device for detecting the acceleration of the pylon is
provided as the device for ascertaining the oscillation travel and
the oscillation travel of the pylon is ascertained from the
detected acceleration.
13. A wind power installation according to claim 12 characterised
by a device for monitoring the device for detecting accelerations
of the pylon.
Description
[0001] The present invention concerns a method of controlling a
wind power installation having a control apparatus for operational
management of the wind power installation, in which the
acceleration of the pylon is detected. The invention further
concerns a wind power installation comprising a pylon, a control
apparatus for operational management of the wind power installation
and a device for detecting the acceleration of the pylon.
[0002] Disposed at the top of the pylon of a wind power
installation of the horizontal-axis type are the generator, the
entire drive train and the rotor, that is to say all movable parts
of the wind power installation, which take energy from the wind and
convert it into electrical energy.
[0003] Conversion is effected by the rotor being caused to rotate
by the wind and by that rotary movement being transmitted to the
generator or generators. Therefore the speed of rotation is
dependent on the one hand on the wind and on the other hand on the
aerodynamic properties of the wind power installation.
[0004] It will be seen from the foregoing that the pylon must
therefore not only carry the rotor, the drive train and the
generator (and the pod) but in addition it must also securely
withstand the loadings which act thereon in operation. In addition
the pylon must withstand high wind speeds, even if the wind power
installation is already out of operation.
[0005] DE 33 08 566 and corresponding U.S. application U.S. Pat.
No. 4,435,647 disclose a wind turbine installation in which
arranged on the pylon is a motion measuring device which generates
a motion signal, depending on how the top of the pylon is moving in
operation.
[0006] DE 100 11 393 discloses a regulating system for a wind power
installation, having means for the detection of measurement
parameters which permit direct or indirect quantification of the
current turbine loading and/or stressing which are dependent on
location and weather, and a downstream-connected electronic signal
processing arrangement which makes it possible for the reduction in
power required in optimised wind power installations to be limited
to the economic optimum which corresponds to the current operating
conditions, in the range of the nominal wind speed and at high wind
speeds.
[0007] DE 100 16 912 discloses operational management of offshore
wind power installations, which is dependent on the natural
frequency of the pylon, wherein firstly the respective critical
natural frequencies of the installation and/or parts of the
installation are determined, and thereafter the rotary speed range
of the rotor in which excitation of the overall installation and/or
individual parts of the installation occurs in the range of the
critical natural frequencies thereof is determined, so that the
wind power installation is operated only below or above the
critical rotary speed range, passing quickly through the critical
rotary speed range.
[0008] Therefore, given load situations in respect of which the
pylon must be designed are derived from those loadings. Such loads
are referred to as dimensioning loads and thus determine the
dimensioning of the pylon. In turn, that dimensioning procedure
also affords the oscillation characteristics of the pylon, its
natural frequencies (the fundamental frequency and harmonics
thereof) and so forth.
[0009] Now, for wind power installations there is a series of
regulations which they have to observe. That also includes a
`Directive for Wind Power Installations`, issued by the `Deutsche
Institut fur Bautechnik (DIBt)` [`German Institute for Construction
Technology`] in Berlin. That Directive sets forth inter alia a
regulation regarding operational oscillation monitoring of the
pylon. Accordingly, in an operating range in which the excitation
frequency of the rotor is in a band width of the natural frequency
of the pylon +/-5%, permanent operation without operational
oscillation monitoring is inadmissible.
[0010] Therefore the object of the present invention is to develop
a method and a wind power installation of the kind set forth in the
opening part of this specification, in such a way as to implement
reliable and efficient oscillation monitoring in order to open up
the above-mentioned frequency range for operation of the wind power
installation.
[0011] According to the invention that object is attained by a
method as set forth in claim 1 and a wind power installation having
the features as set forth in claim 11. Advantageous developments
are described in the appendant claims. The invention is based on
the approach of not only detecting the oscillation frequencies--as
in the state of the art--but in particular also the oscillation
amplitudes, that is to say ascertaining the oscillation travel.
Finally a wind power installation can be also operated in a
critical frequency range as long as there the oscillation
amplitudes do not exceed a given limit value.
[0012] The invention is based on the realisation that, in regard to
all non-forced oscillations of the pylon, the oscillations at the
first natural frequency of the pylon involve the greatest amplitude
and thus represent the greatest loading for the pylon. Oscillations
with harmonics of the first natural frequency are always of smaller
amplitudes. Components of accelerations with a harmonic of the
first natural frequency of the pylon, which have an influence in
terms of ascertaining the oscillation travel but which admittedly
are of a smaller amplitude, are however incorporated into the
calculation on the basis of the first natural frequency and are
therefore overvalued.
[0013] This means that the oscillation travel is substantially
proportional to the loads and the loads derived from the
oscillation travel are rather higher than the loads which actually
act. The loads are therefore overvalued rather than undervalued.
Load detection therefore affords an increased level of
security.
[0014] In the case of oscillations which are parallel to the plane
of the rotor and are therefore forced, the frequency of the
oscillation can be significantly below the first natural frequency
of the pylon. In that case, ascertaining the loading on the basis
of the first natural frequency of the pylon is certain to result in
undervaluation of the oscillation travel. In order to avoid that
undervaluation the oscillation frequency is monitored in on- going
operation and if necessary used for ascertaining the oscillation
travel with a corrected value.
[0015] When an oscillation travel which exceeds a first limit
value, which therefore exceeds a first load, is ascertained, a risk
situation is recognised and the control apparatus reacts thereto. A
risk situation is likewise recognised if a second limit value in
respect of the oscillation travel is exceeded within a
predeterminable period of time. In order reliably to eliminate that
risk situation the installation can be stopped.
[0016] In addition the object of the invention is attained by a
wind power installation as set forth in the classifying portion of
claim 10, characterised by a device for ascertaining the
oscillation travel from the detected acceleration levels. That
ascertained oscillation travel is then processed or evaluated in
accordance with the method of the invention.
[0017] In a preferred development of the invention the wind power
installation includes a device for monitoring the device for
detecting levels of acceleration of the pylon. It is possible in
that way to detect a failure on the part of oscillation monitoring
and it is possible to initiate measures for eliminating the fault
and for stopping the wind power installation so that oscillations
cannot uncontrolledly occur.
[0018] Further advantageous embodiments of the invention are
recited in the appendant claims.
[0019] An embodiment of the invention is described in detail
hereinafter with reference to the drawing in which:
[0020] FIG. 1 shows a plan view of the pod with two acceleration
sensors, and
[0021] FIG. 2 shows a flow chart of the control process in a first
embodiment of the invention.
[0022] The plan view in FIG. 1 shows a pod 10 from which rotor
blades 12 laterally extend. The pod is arranged at the top of a
pylon 16. Disposed in the interior of the pod 10 is a measuring
device 14 with two acceleration sensors. Those acceleration sensors
are oriented in a horizontal plane and are at a right angle to each
other. By virtue of that arrangement, it is possible to detect
pylon oscillations in the corresponding directions, that is to say
on the one hand substantially parallel to the rotor blade plane and
on the other hand perpendicularly to the rotor blade plane.
[0023] Oscillations at the natural frequency of the pylon 16, which
are excited for example by wind loads, are always oscillations in
perpendicular relationship to the plane of the rotor, which are
detected by a suitably oriented acceleration sensor 14. Forced
oscillations which can occur for example due to unbalance at the
rotor are oscillations which take place substantially parallel to
the plane of the rotor. They are detected by a second acceleration
sensor 14. In that case, such forced oscillations do not in any way
take place at the first natural frequency of the pylon 16 or a
harmonic thereof. They are forcibly imposed on the pylon 16 and can
achieve such high amplitudes that an immediate shutdown is
required.
[0024] In that respect monitoring of the oscillation travel in
perpendicular relationship to the plane of the rotor also permits
monitoring of the control of the angle of incidence of the rotor
blades for, when the control of the rotor blade angle of incidence
is operating satisfactorily, the oscillation characteristics of the
pylon differ considerably from the oscillation characteristics when
the control is not operating properly. Therefore, when the control
of the rotor blade angle of incidence is not operating
satisfactorily, oscillations also occur, which can result in
shutdown.
[0025] The ascertained oscillation data can also be linked to the
wind direction data so that it is also possible to ascertain a
relationship as to whether greater oscillation travels have
occurred when given wind directions are involved, than when other
wind directions occur. Finally under some circumstances the
landscape geography around the wind power installation also has
effects--with the wind speed remaining the same--, depending on the
direction from which the wind is blowing.
[0026] FIG. 2 shows a flow chart which illustrates the procedure
involved in the method according to the invention of controlling
the wind power installation. The procedure begins with step 20.
Subsequent step 22 involves detection of the oscillation of the
pylon by the acceleration sensors 10, 14. Oscillation detection is
effected for a period of time of 20 seconds. In that case, all
accelerations are cumulated in those 20 seconds. After the expiry
of that period of time, the effective value of the oscillation
travel at the height of the hub is calculated from the sum of all
accelerations and the first natural frequency of the pylon, in
accordance with the formula S(eff)=a(eff)/?.sup.2. Therein S(eff)
is the effective value of the pylon oscillation travel, a(eff) is
the effective value of all accelerations over a time interval of 20
seconds and u.sup.2 is the square of 2?f, wherein f represents the
first natural frequency of the pylon. The value of S(eff) is then
multiplied by v2 in order to obtain the oscillation amplitude, that
is to say the average deflection of the pylon from the rest
position.
[0027] The first natural frequency of the pylon is generally
relatively precisely known by measurements or calculations so that
this value is firstly used for calculation of the oscillation
travel when the installation is freshly brought into operation. As
however the actual natural frequency of the pylon can deviate from
the theoretical value in dependence on manufacture-induced
tolerances in terms of the stiffness of the pylon or different
kinds of foundations, the natural frequency of the pylon which is
used in the calculations is gradually corrected by the control
apparatus when pylon oscillations occur, by assessment of the
period duration of the signal from the acceleration sensors. In
that way measurement of the oscillation travel is adapted to the
respective conditions of an installation.
[0028] For the further progress of the method, a series of limit
values are also established, which are taken into account in the
context of evaluation of the detected oscillation travel. A first
limit value S.sub.max determines a maximum admissible oscillation
travel. Let this be 500 mm in the present example. A second limit
value defines a minimum admissible oscillation travel S.sub.min.
Let this be 220 mm in the present example. A third limit value
determines the shutdown limit and is always used as a shutdown
criterion when admittedly the first limit value S.sub.max is not
exceeded but the second limit value S.sub.min is exceeded. That
third limit value is identified as S.sub.grenz and its numerical
unit-less value is for example 1 612 800.
[0029] Step 23 of the flow chart in FIG. 2 now involves checking
whether the ascertained oscillation travel exceeds the first limit
value S.sub.max. If that is the case in step 29 the installation is
immediately stopped and the procedure is halted.
[0030] If the checking operation in step 23 shows that the
oscillation travel does not exceed the first limit value S.sub.max,
then step 24 of the flow chart involves forming the sum of the
squares of the total oscillation travels. For that purpose the
oscillation travel S detected in the time interval is squared and
the square of the second limit value S.sub.min, that is to say
S.sub.min.sup.2, is subtracted therefrom. The resulting difference
is added to the sum already ascertained in the preceding
intervals.
[0031] That affords shutdown of the installation at the earliest if
the measured oscillation travel over 8 measurement intervals is
equal to the maximum admissible oscillation travel S.sub.max.
Oscillation travels which are between the minimum and the maximum
oscillation travel result in an overproportional curtailment of the
shutdown times due to the square sum formation and the dependency
of the amplitude of the oscillation travel. If the value falls
below the minimum oscillation travel (second limit value
S.sub.min), the sum of the oscillation travel squares falls. If now
the third limit value S.sub.grenz is reached or exceeded by the sum
of the squares, the installation is again stopped.
[0032] It is also possible, instead of the installation being
stopped immediately, for it to possibly also be operated in such a
way that the first limit value S.sub.max thereafter immediately
falls. For that purpose it is possible for example to implement
adjustment of the rotor blades or to turn the pod out of the wind
(store). One measure can also be that of increasing the rotor blade
speed so that the installation passes out of the critical range of
its natural frequency.
[0033] The present application refers in particular to the use of
acceleration sensors for ascertaining the oscillation travel
(oscillation amplitude). It is also possible to use other devices
to ascertain the oscillation travel (amplitude). If necessary the
man skilled in the art will make use of a device which is suitable
for the respective use. As an alternative to the acceleration
sensors and as an alternative to ascertaining the oscillation
travel by means of acceleration sensors, it is also possible to
implement optical measurement, although here that is usually quite
expensive.
[0034] As an alternative to an acceleration measuring device, it is
also possible to establish the oscillation of the pylon under some
circumstances by resistance strain gauges at the base of the pylon
of the wind power installation. For that purpose at least two
resistance strain gauges should be mounted at the region of the
base of the pylon displaced relative to each other approximately
through 90.degree.. Such resistance strain gauges can not only
detect the elongation but also the compression of the material. In
that respect, the greater the oscillation amplitude of the pylon,
the greater is also the corresponding elongation/compression in the
region of the resistance strain gauges which are preferably
oriented in the main direction of the wind of the wind power
installation. Such resistance strain gauges can be used not only to
measure loadings on the pylon in the region of the base thereof,
but also to derive the magnitude of the deflection of the pylon in
the region of the pod or the top of the pylon, as the loading in
the region of the base of the pylon also increases depending on the
respective amplitude of deflection movement of the top of the
pylon. It will be appreciated that the above-described resistance
strain gauges (or another sensor which detects the loading on the
pylon) could also be disposed in other regions of the pylon, for
example also at a mid-height position on the pylon.
* * * * *